PROJECT SUMMARY Depression and anxiety disorders are highly comorbid and rank in the top ten causes of years lived with disability. Current gold-standard treatments are effective but do not work as well as we would like, with less than 50% experiencing long-lasting improvements. Two gold-standard behavioral interventions for depression and anxiety include behavioral activation, focused on enhancing approach behavior towards meaningful and reinforcing activities, and exposure-based therapy, focused on decreasing avoidance and challenging negative expectations through exposure to anxiety-provoking cues or situations. While these interventions have divergent approach versus avoidance treatment targets, there is currently little knowledge to guide clinical decision-making, i.e., to inform which strategies should be provided in the frequent case of comorbid anxiety and depression symptoms. Approach-avoidance decision-making paradigms focus on assessing neural and behavioral responses when faced with potential rewards and threats, tapping into processes though to be important for both anxiety and depression as well as behavioral activation and exposure-based therapy. For this study, we will recruit individuals reporting both anxiety and depression symptoms and randomize them to one of three different psychotherapeutic interventions delivered in a group setting, including (1) behavioral activation, (2) exposure-based therapy, and a non-specific therapy approach (3) supportive therapy. Participants will complete clinical, self-report, behavioral, and functional magnetic resonance imaging (fMRI) assessments before and after therapy. Clinical symptoms will also be assessed three and six months following therapy completion. We will use a computational approach to model the different factors that may influence one?s behavior during approach-avoidance decision-making, including drives to avoid threat versus approach reward and confidence versus uncertainty in one?s decisions. This project will accomplish the following aims (1) Determine how changes in brain and behavior responses during approach-avoidance conflict relate to changes in mental health symptoms with the different therapy approaches, (2) Determine the degree to which baseline brain and behavior responses during approach-avoidance conflict predict response to the different therapy approaches, above and beyond the influence of demographics and baseline symptom severity. Results will have enhance our understanding of how different psychotherapy approaches (behavioral activation, exposure-based therapy) may impact brain responses and decisions when faces with potential reward versus threat and approach versus avoidance drives. In addition, results will have important implications concerning the potential for a more personalized approach to psychotherapy, enhancing knowledge of which types of therapy strategies may be most beneficial for which individuals.